Electric motors are generally known and comprise a stator and a rotor, which can be rotated relatively to the stator, the rotor driving or forming a drive shaft of the electric motor, by means of which the drive power at the electric motor can be tapped. Electric motors are divided into direct-current electric motors, DC motors for short, and alternating-current electric motors, AC motors for short. Furthermore, internal rotors, with which the rotor is arranged concentrically in the stator, and external rotors, with which the stator is arranged concentrically in the rotor, are differentiated from one another. Finally, contactlessly commutated electric motors are differentiated from contact-commutated electric motors. Contact commutation takes place via a physical or mechanical contact by means of at least one contact element, which to this end bears directly on a sliding contour and creates an electrical connection. The contact element can also be termed a “brush”. Generally, a contact element of this type has a contact body made from carbon. In contrast, a contactless commutation takes place electronically, that is to say by means of corresponding electronics or an electrical circuit.
Electric motors are used in virtually all areas of technology. In particular, electric motors are also used for vehicles, in order to adjust movable actuators. By way of example and without limiting the generality, mention may be made here of a throttling device with a throttle as actuator, which can be adjusted with the aid of an electric motor, in order to set the throttling of the fresh-air flow in a ventilation system of an internal combustion engine. Furthermore, flap devices are conceivable, in which at least one flap can be adjusted with the aid of an electric motor, for example in order to influence the feeding of fresh air into a combustion chamber of the internal combustion engine. Furthermore, electric motors can be used in a turbine of a charging apparatus, preferably in an exhaust turbocharger, for example in order to actuate a wastegate valve or to actuate a variable turbine geometry.
In automotive uses in particular, the respective electric motor can be exposed to a comparatively large thermal load, as a result of which the durability or the expected service life of the respective electric motor is reduced.
An increased thermal load is produced in particular also in uses, in which the electric motor must hold an actuator counter to a restoring force, so that in the respective coil arrangement, the entire electrical power is converted into heat, which cannot or can only be poorly dissipated in a warm or hot environment.